I've been trying to download the ISO for Server 12.10 amd64 for a week now. None of the MD5 checksums match the posted values. I am not having any problems downloading from other sites, and I've tried the download from multiple computers.

Try torrenting the files from the .torrent files on the site. The BitTorrent protocol has built in file checking, so your likelihood of a corrupted download is much lower - plus, file download speeds will most likely be faster!